Process for separating hydrocarbon oils



May 14, 1940. E, B'slNG PRocEss Fon SEPARATING HYDRQCARBON oILs Filed Aug. 1,7. 1938' /n ven zor Erbs( 'szhy i @y M7 mail@ Hfs Afomeys.

Patented May 14, 1940 v 2,201,120 Pnocnss Foa snragrmc mnocmon Ernst Bsing, Bel'lll,`

Germany, assignor `to Edeleanu Gesellschaft, m. b. Il., a corporation of Germany Application August 17,

193s, serial No. 225,463

In Germany August 31, 1937 9 Claims.

This invention relates to the separation of hydrocarbon mixtures such as crude oils, residual oils and distillates derived therefrom. Morey speciiically, the invention relates to a process in which unrened hydrocarbon oils are cooled in the presence of active diluents to such a low teln-i perature, e. g. F. or lower, that the high viscosity constituents, which are valuable vfor lubricating purposes and which are contained in 10 said hydrocarbon oils, are separated in a readily llterable form.

It is already known to dissolve. wax-containing hydrocarbon oils in such diluents as low boiling hydrocarbons, ethers or others, and to cool the f solution to a low temperature in order to precipitate and remove the wax therefrom. It has also been proposed to use in similar processes `mixtures or blends of solvents, of which one solvent is selective towards certain groups of oil constituents and the other solvent is non-selective,

that is, one which exerts no selective solvent action on any group of hydrocarbon oil constituents. The rcomposition and proportions of such -solvent mixtures or'blends, as disclosed for this y purpose in the prior art, are however, always selected in such 'manner that their components are miscible even at very low temperatures in one liquid phase, and a separation of the oil-solvent mixture into two phases is carefully avoided.

I have discovered that, in contradistinction to the known practice, a solvent blend may be employed to prepare the oil-solvent mixture forseparation into high and low quality fractions, which solvent blend comprises both a selective solvent and a non-selective solvent and in which part of the non-selective solvent solidiiles at the low temperature of treatment and assists in the removal of the high quality oil constituents from the mixture, i. e., acts as a separation aid. Benzol 06H6, for example, is such a suitable nonselective solvent. It will be understood that my invention also comprises the treatment of wax A containing oils, in which case the wax separates out in the cooled oil-solvent mixture, along with d some of the benzol, and both wax and benzol function as separation aid for the high quality oil.

It is already known in the art of dewaxing hydrocarbonoils to employ a blend of a selective solvent, having a low melting point such as ace-- tone, and a non-selective solvent, having a comparatively high melting point such' as benzol, to dissolve the wax containing hydrocarbonoil in said solvent blend, cool the mixture to a low temperature and remove the solidified wax therefrom. In these known processes, however. the

'composition of the solvent blend is always selected in such manner that the normally liquid high quality oil constituents remain homogeneously dissolved and that only the wax, containing a comparatively small amount of liquid oil constituents of relatively highviscosity index, separates out as a solid phase.

The hydrocarbon oil which may be rened according to my invention, may be a crude oil, a residual oil or a distillate derived from mineral oils, coal tar oils, cracked oils or from oils pro- -duced synthetically. t

In the practice of my invention the hydrocarbon oil to be rened is mixed with a solvent blend, preferably of such composition that at *he temperature of mixing, all of the hydrocarbon oil constituents are dissolved, and which can be strongly cooled without becoming viscou's. 'I'his solvent blend comprises al solvent which exerts a selective solvent action only upon the low quality o'il constituents of the hydrocarbon oil and which remains liquid at the low treating temperature; and it comprises a second solvent which isv not selective towards anygroup of hydrocarbon oil components, and which has a melting point so high that it solidies partly at the low treating temperature. l

Examples of selective solvents suitable for carrying out my invention when mixed with one or more non-selective solvents, are liquid sulphur dioxide, pyridine CsHsN, mixtures of pyridine and its homologs for example a, 'y picolines (CH3C5H4N) acetone, rluorine derivatives of low boiling hydrocarbons of the parailin series, such as difluoromethane CHzFz, trifluoro-ethane CHFa-cHzF, mixtures thereof, and others.

Representatives of the non-selective solvents which are operative in my process are benzol, dihydronaphthalene and others. 1, 4 dihydronaphthalene has a melting point of F. and a boiling point of 414 F. Generally speaking, any auxiliary solvent which is entirely miscible with the selective solvent as well as with the hydrocarbon oil and which solidilies partly at the illtration temperature, having preferably a melting point of about 30 F. or above, will work for the purpose. described.

Instead of using one non-selective solvent of the type described, in mixture with the selective solvent, I may also employ a mixture containing the selective solvent and two non-selective solvents of which one has a comparatively high melting point and the other a comparatively low melting point. A blend of benzol and tetrationed as an example; benzol has the comparatively high meltingpoint of +42 F. andntetralin solidifles only far below 0 F.

In carrying out my process I dissolve the hydrocarbonV oil in a blend oi'l a selective solvent and one or more non-selective solvents, at least one of which has a comparatively high melting point, and thereupon the homogeneous solution, f thus obtained, is cooled toa low temperature.

` The respective quantities of selective and nonselectivesolvents are chosen in`fsuch manner that a phase separation between the high and low qualityconstituentsoi the oil is obtained at the low temperature and that part of the nonselective solvent crystallizes out. I have discovered that this crystallized non-selective solvent functions as' an adsorption medium for the high quality oil constituents which are being separated out of the solution as an undissolved phase due to the selective action of the solvent blend.- .The

undissolved phase, comprising the high qualityl oil components and the crystallized non-selective solvent, is separated by settling or preferably by iiltration from the dissolved phase containing the low quality oil components dissolved in the bulk of the remaining solvent blend.

When ling the iiltration methodiorseparating the undissolved phasev from the dissolved, phase, continuous rotating drum snltersy may preferably be employed. The undissolved phase is thereby obtained as a filter cake and this cake is `readily washed with a diluent blend of the same or'similar composition as that remaining inthe -ltrate solution. -In most cases washing of the cake can be eliminated. The cake is remo'ved from the lter and is heated to'recover by distillation the diluent or diluents contained A therein.

Instead of using the distillation method for solvent recovery, I may employ a solvent for washing the diluents out of the undissolved phase.

As compared with other hydrocarbon oils, the inven ion described herein recesses of rening"` has the advantage that the non-selective solvent or separation aid may be easily removed from f. i. SO2, and a non-selective solvent, f. i. benzol;

and containing the non-selective solvent in such quantities that a homogeneous solution is just obtained at normal temperature.` Upon cooling this homogeneous solution, part oi the benzol or other non-selective solvent solidifies and separates out as a solid. Consequently, the remaining liquid solvent mixture becomes more selective, due to Ithe action of the liquid SO2, and the previously homogeneous oil-solvent solution yseparates into two phases, one of which contains` the bulk of the solvent blend and dissolved therein lthe low quality oil constituents, and the' other contains the solid benzol and. included therein or* solvent constituent soliditles.

. lin (tetrahydronaphthalene) -C1oH1z may be mencommingled therewith the ligh quality oil constituents or rened oil. f

new process `may be carried out in several steps instead of in one, as described, and it may also be combined with other rening methods. u

To illustratevmy methodof operation I refer tothe appended ilow diagram which -shows an operating cycle comprising a normal dewaxing step followed by two oil separation steps.'`

Tank l contains the waxy oil to be processed. Tank 2 serves as storage for the selective solvent land tank 3 contains the non-selective solvent.

'I'he oil ows from tank I tobranch i and is diluted with a solvent mixture having one com- 7 ponent of the non-selective type towards the oil phase and another component of the selective type. The solvent mixture is so adjusted that during the rst illtration step -a complete solvent .action is exerted upon the Anormally liquid oil constituents since lthis step of operation represents a normal dewaxing process.. :The proper blending of the two solvent -components is accomplished at points i8 anddl. The mixture of dewaxing solvent and' oil enters heater I wherein the fluids are warmed up until a homogeneous solution results. leaving heater 5 the mixture is cooled in chiller l by means of a lelatively cold extract-solution whose source o1' origin will be described later. l

'In chiller 6 the wax is precipitated from a homogeneous solution oi oil and solvent and the cold mass ,ows' into lter 1 wherein wax and oil are separated in a conventional manner. The

iilter-cake resulting -from this operation is -washed with solvent of the same composition as the diluent solution. This wash-solvent is branched oil! from the mixed-solvent line at point 33 to be conducted to solvent cooler 34 and from there on to illter 'l through line 35. Filtration is carried out at vconventional dew temperatures, for example from --10 to 0 F.

The illtrate solution obtained from ,this operation is now pumped through a low temperature v chiller 8, wherein- `the solution is cooled tosuch an extent 4that a portion of the non-selective 'Ihis enriches the concentration of the selective solvent in the remaining lliquid phase, causing thereby precipitation of relatively high quality oil fractions which adhere to the non-selective solvent crystals to form a readily lterable mass of high quality oil' fractions and solid solvent as a filter-cake in illter 9. This iilter-cake may be washed with a solvent mixture of essentially the same composition as is .now in equilibrium With the 011 in the ltrate from this operation,l but .with most of the oils treated the washing step can be eliminated.L

The oil-solvent-.crystal cake is removed through line 29 to still 30 wherein the'solvents .are recovered through lines I6 and l1 to flow to their respective storage tanks 3 and 2. Since the solvent crystals also-retain a small amount of selective solvent, provisions are made at the column to recoverl both separately. If, for example, a pyridine type solvent is used -as the selective component and benzol as the non-selective constituent, the `benzol is recovered at the top ofk the towerfwhereas thepyridine is recovered from a tray as a side out. i. e. through lines I1.` The still bottoms represent-the solvent-freel finished high-quality oil fractions vwhich ilow through line 3l to storage tank 32,l

The fllter-cake from the first-filtration step in lter 1 represents 'of course a normal wax-cake. u

. f cake is removed throughline 25 to still 26 to recoverthe solvents as previously described through lines I6 and I'I. The solvent-free wax is withdrawn from the bottom through line 21 into storage tank 28.

Continuing the process cycle from filter `il, the filtrate obtainedduring the oil-separation step in filter 9 comprises a mixture of mixed solvent and oil fractions richer in naphthenicwconstituents than the original oil since part of the highl quality oil fractions have been removed as previously explained. The residual solvent composition now contained in the solution has changed to such an extent that the selective'component dominates since the non-selective solvent was partly removed in filter 9 with the high-quality oil fractions asv a filter-cake. It is, therefore, essential to add a new quantum of non-selective solvent to the filtrate solution from filter 9, approximately equal to the amount removed together with the high-quality oil constituents prior to repeating the oil separation step over lter I2.

The new quantum of non-selective solvent is obtainedv fromy storage over branch I9 through line 20 and is admitted to the filtrate coming from filter 9 at mixer I0. mixture s forced through Chiller II wherein the temperature is again lowered `a few degrees for .the purpose of precipitating more oil of higher quality together with non-selective solvent `crystals, whereupon the cold mass is forced over filter I2 to separate into a solid phaseand a'liquid phase.

The filtrate contains now oil constituents Tof relatively naphthenic characteristics and this solution may be batch' extracted by means of modication of the rsolution with water if the solvent Y solution comprises pyridine and benzol, whereupon a heavy asphaltic extract lsolution may be obtained on the one hand and a relatively 10W grade oil vfraction on the other hand'. This process step of batch extractiony is optional and is not indicated in the fiow diagram since/itis apparent from the drawing that the total filtrate from filter I2 is caused to ow through jline I3 to chiller 6 to cool a new charge of stock entering dewaxing filter `I. From chiller 6 the iiuid is conducted through line Il to still I5 to recover oil and solvents. The solvent constituents are separately collected and conveyed to their respective storage tanks whereas the naphthenic or extract oil is run to storage tank 24.

The filter-cake produced in filter I2 is composed of non-selective solvent crystals and higher quality oil components as previously described and this cake is separated into components in column 22 to-which it is conducted through line 2i. Solvents are recovered through lines I6 and II and the'refined oilwfiows to storage tank 23.

The drawing shows the process diagrammatically only and; therefore, no auxiliary devices such as valves, pumps, flow meters etc. are indicated.

Example 1 A lubricating oil distillate containing 20% wax and with properties as shown in the table below, was mixed with 200 vol. of a diluent blend comprising 40 volbenzol and 60 vol. pyridine. The pyridine, which was used in this instance, was a so-called technical or commercial pyridine boiling substantially up to 293 F. maximumand containing mainly higher homologs of pyridine. The pyridine was further dried, prior to its use, and its water content was 0.08%.

` The oil-diluent mixture was then cooled to Leaving mixer I the 22 F. whereby the wax separated out which could thereupon be removed from the oil-diluent mixture by filtration. The filtrate, that is the oil-solvent mixture, was further cooled to 40 F. but no appreciable formation of solid particles occurred. A separation of solid matter could also not be effected by the addition of small quantities of water; the water caused merely a -phase separation as could be observed. Thereupon further quantities of benzol were added to the filtrate, namely 60 vol. of the amount of benzol first used, and this caused'the separation of a crystalline mass at 40 F., which could again be removed from the remaining oil-solvent solution by filtration. The filter rate thereby obtained was extraordinarily high. Upon melting the low temperature filter cake it was found to consist of benzol and light coloured lubricating oil of improved characteristics both of which l were separated from each other by distillation.

The filtrate obtained `by filtration at the low -temperature of 40 F. yielded an `oil of low quality.

The following table gives theresults obtained, the viscosity index of the original oil, after having been dewaxed in a conventional manner, was determined to be 60 and this value is shown for comparison in brackets in the first column of the following tabl'e:

`The wax'containing lubricating oil distillate used in Example 1, was treated in this case with 250 vol. of a benzolpyridine blend containtaining equal volumes of benzol and pyridine. The solution was again cooled to 22 F., freed from the separated waxby filtrationand the dewaxed oil solution was then further cooled to.

40v F. whereby a separation into two phases occurred and a filterab'le mass, containing 4solid benzol and high quality oil constituents, `herein called low temperature raffinate I, was pro-- duced. This mass of benzol crystals and low A temperature raffinate I was separated fromthe oil-solvent mixture by filtration. To the remaining solution was then added about as much benzol as was contained in said low ltemperature raflnate I, and the solution was thereupon'further cooled to 53 F. As a consequence of -the addition of vbenzol and of the further reduction of temperature to 53 F.- additional amounts of benzol crystallized out and in it lubricating oil constituents were found again. vThis second crystallization and fractionation product is herein referred to as low temperature raffinate 11; it was again separated from the solution, and the latter was one more mixed with benzol and cooled to 53 F. A third separation product (low temperature raffinate III) was obtained containing again benzol in crystallized form and commingled therewith an oil, the quality of which was not as good as that obtainedwith the first and second separation products because with these products (low temperature raffinate I and II) all the high quality lubricating oil had already been removed from the original distillate.

'rlie solvents, including "the crystallized benzol, contained in lowv temperature raiinates Ito III,

were recovered by l distillatiom. and likewise the wax cake above mentioned and the final low temperature iiltrate were freed from the benzol and pyridine contained therein; and -a series of products resulted from the entire treatment with yields andl characteristics as shownin theappended table:

It will be'evident from thedisclosure'of myin-v vention and from the=examples that I` have de- 'vised a process suitable for the separation oi.'

high quality oil constituents from a hydrocarbon oil mixture containing the same along-with low quality oil constituents, andthat myprocess is suitable for reiining wax containing oils as well as wax-free oils.' i

' VI do not limit'myself to the procedure described ture containing the same together with low quality oil constituents. comprising .dissolving said mixture in a ,solvent blend consisting ofV a selective solvent having a low melting point and a non-selective solvent having a melting point of not less than '30 F., the volumetric composition of said solvent blend being such that upon cooling to a low temperature a substantial amount oi' the non-selective solvent will crystallize out as a solid and the remainder of said solvent blend .wll become selective towards the low quality oil constituents, cooling said solution of hydrocarbon mixture and solvent blend to a low temperature to crystallizeout part o! said non-selective solvent and to form a heterogeneous wax-free mixture comprising an undissolved phase containing solid non-selectiveV solvent and thev liquid high -qualityoilconstituents, and a dissolved phase containing the remainder of fsaid solvent blend in liquid form and dissolved therein the low quality oil constituents; separating the undissolved phase from the dissolved phase and re- Ycovering the solvents from both phases.

2. A process'of separating hydrocarbon mix.- tures comtaining high and low quality oil constituents and wax, comprising dissolving said mixture in 'a solvent blend consisting of a selective solvent having a low melting point and a non-selective solvent having a melting point oi not less than F., the volumetric composition of said solvent blend being vsuch that upon cooling to F. or lower a substantial amount of the non-selective solvent will crystallize out as a solid and the remainder of said solvent blend will become selective .towards the low quality oil con- Lstituents, cooling the solution of said hydrocarbon mixtures in said solvent blend'to a temperature of substantially 20 below zero F. whereby only the wax separates out as a solid phase, re-

phase from the moving said-wax from the solution, cooling thev latter to substantially 40 below zero Fahrenheit to crystallize out part of the non-selective solvent and to form an undissolved phase containing solid non-selective solvent and the liquid high 6 .quality oil phase, and a dissolved'phase con-` taining, the remainder of said solvent blend in liquid form and dissolved therein they low quality oil constituents, separating theundissolved the solvents from the solid wax phase and from the undissolved and dissolved phases.

3. A process of separating hydrocarbon mix'- ltures containing high and low quality oil constituents and wax, comprising dissolving said mixture 1I in a solvent -blend consisting of a selective solvent Q having a low melting point and a non-selective solvent having a melting point of not less than 30 F., the volumetric composition of said solvent blend being such that 'upon cooling to 40 F.. 90

or lower a substantial amount of the nonselective solvent will crystallize out as a solid and the remainder of said solvent blend'willbecome selective towards the low quality oil constituents,

,cooling the solution of said hydrocarbon mixtures 25 in said solvent blend to a temperature oi substantially 20 F. whereby only the wax -separates out as a solid phase, removing said wax from the solution, adding to the latter an additional. quantity of said non-selective solvent, cooling the mix- 30 ture to substantially 40 F.- to crystallize out part ofthe non-selective solvent and to form an )undissolved phase containing solid nonselective solvent andthe liquid high quality oil phase, and

a dissolved phase containing the remainder of said l5 solvent blend in liquid form and dissolved therein the low quality oil constituents, separating the'. undissolved phase from the dissolved phase and recovering the solvents from the solid wax phase and from the undissolved and dissolved phases. 40 4. A process oni' producing a lubricating oil of high quality from wax-free hydrocarbon mixtures containing the same together with low 'quality ,oil constituents in accordance with claim 1in which the selective solvent consists oi a sub- 45. stance of the vclass of pyridine and its homologs and in which the non-selective solvent consis oi' benzol.

5. A process of separating hydrocarbon mixtures containing high and low quality oil con- 5u stituents and wax in accordance with claim 2 in whichthe selective solvent consists of a substance of theclass of pyridine and its homologs and in which the non-selective solvent consists of benzol.

and the solvent blend contains equalvolumes of said substance and of benzol.l

6. A process of separating hydrocarbon mixtures containing high and low quality oil constituents and wax, comprising dissolving said mixture in a solvent blend consisting of a selec- 00 tive solvent having a low melting point and a -nonselective solvent having `a melting point of not less than 30 F., the volun tric composition ofsaid solvent blendA being such hat upon cooling to 40 F. or lower a substantial amount of c5 the non-selective solvent will crystallize out as a solid and the remainder of'said solvent blend `will become selective towards the low quality oil constituents, cooling the solution of said hydrocarbon mixtures in said solventblend to a temperature of substantially 20 F. whereby the` wax separates out as a solid phase, removing said wax from the solution, and cooling the latter to I substantially 40 F. to crystallize out part of `the non-selective solvent and to form an undis- 16 dissolved phase and recovering 10 -mi; said hydrocarbon mixture with a solvent solved phase `containing 'solid non-selective solvent and high quality oil constituents, and a dis- ,solved phase containing the remainder of said solvent blend in liquid form and dissolved therein low quality oil constituents, separating the undissolved phase from the dissolved phase, adding to the latter an additional quantity of said nonselective solvent and cooling the mixture to substantially -53 F. to obtain a second undissolved phase containing solid non-selective solvent and high quality oil constituents, and a second dis`- solved phase containing the remainder of the solvent blend and dissolved therein low quality oil constituents, separating the second undis- 'solved phase from the second dissolved phase and recovering the solvents from-the solid wax phase. from the rst and second undissolved phases and from the second dissolved phase.

17. A process as claimed in claim 6 in which the selective solvent consists of a substance of the class of pyridine and its homologs and in which the non-selective solvent consists of benzol.

8. A process of separating high quality lubrieating oil constituents from a wax-free hydrocarbon mixture containing the same together with low quality oil constituents, comprising mixblend consisting of a selective solvent having a low melting point and a non-selective solvent which will partly solidify at the separating temperature, said solvent blend having a selective solvent action for the low quality oil constituents and having substantially no solvent action for the high quality oil constituents at temperatures below zero degrees Fahrenheit, cooling the mixture of said high and low quality oil constituents and said solvent blend to below zero degrees Fahrenheit to produce a heterogeneous wax-free mixture comprising an undissolved phase containing solidl non-selective solvent and substantially all of. the lliquid high quality oil constituents, and a dissolved phase containing the 'rewhich the non-selective solvent consists of benzol. l

ERNEST BsING; 

